The invention is generally directed to toner compositions, and more specifically, the present invention is directed to developer and toner compositions containing therein charge enhancing additives, which impart, or assist in imparting a negative charge to the toner resin particles. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and the salts of certain spiro-borate compounds as negative charge enhancing additives. The aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, cyan, magenta, yellow, blue, green, red, or brown components and mixtures thereof, thereby providing for the development of black or colored images. The borate salts of the present invention possess a number of advantages including, for example, they are colorless, unlike some dye-based compounds which are of various deep colors. In addition, the borate salts of the present invention are readily solubilized in common organic solvents and are compatible with various toner resins enabling the simple economical processing thereof. Also, the toner compositions of the present invention possess excellent admix characteristics, and maintain their negative triboelectric charges for an extended number of imaging cycles exceeding, for example, 50,000. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. There is also described in U.S. Pat. No. k 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there are disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there are disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014 and 4,394,430.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there is disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271, the disclosure of which is totally incorporated herein by reference, a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.
Other prior art includes Japanese Publication No. 54-145542 which illustrates a negatively chargeable toner consisting of a resin, a colorant, and the charge control agent pyridoxine aliphatic acid ester; East German Patent Publication 218697 relating to liquid developers with charge control additives with structural units of formulas (I), (II) and (III), and which contains olefinically polymerizable bonds; U.S. Pat. Nos. 3,850,642 relating to multilayer sensitive elements wit ionizable salts, acids, esters, and surfactants as charge control agents; 2,970,802 illustrating a composition for the control of hypercholestermia, which composition consists of a nontoxic gelatin containing aluminum nicotinate; and 3,072,659 which discloses a method of preparing aluminum salts of nicotinic acid.
As a result of a patentability search, there were located U.S. Pat. Nos. 4,525,446 relating to a liquid developer with an onium salt polymer and an anion, and more specifically, wherein iodide anions of a quaternized polymer are replaced with tetraphenyl boride anions, see column 7 for example; 4,737,432 directed to a toner with certain borates, such as diorganotin borate; and 4,767,688 relating to a developer with charge-exchange control agents comprising a borate containing an organic anion, including tetraphenylboron anion with sodium or potassium as its corresponding cationic component.
Furthermore, there are disclosed in U.S. Pat. No. 4,623,606, toner compositions with negative charge enhancing additives, the disclosure of which is totally incorporated herein by reference, containing therein as negative charge enhancing additives iron complexes, including the iron complex of azo dyes prepared from coupling diazzotized substituted amino phenols with substituted naphthols.
Although many charge enhancing additives are known, there continues to be a need for new additives, especially those that impart negative charges to toner resin particles. Additionally, there is a need for negative charge enhancing additives which are useful for incorporation into black, or colored toner compositions. Moreover, there is a need for toners containing charge enhancing additives with very light colors thereby avoiding or minimizing impairment of the color of the toner particles. There is also a need for toner compositions with negative charge enhancing additives that possess acceptable triboelectric charging characteristics, and suitable admixing properties. Moreover, there continues to be a need for humidity insensitive negative charged toner and developer compositions. Further, there is a needfor charge enhancing additives which can be easily and permanently dispersed into toner resin particles. There also is a need for negatively charged black, and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally, the toner compositions of the present invention are useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Furthermore, there is a need for negatively charged toner compositions with desirable and rapid toner admix charging characteristics.